Vacuum pump arrangement

ABSTRACT

A vacuum pump arrangement, especially a turbomolecular pump arrangement, comprises a rotor ( 14 ) and a stator ( 16 ) in a pump housing ( 10 ). The pump housing ( 10 ) is connected to a vacuum chamber housing ( 26 ) through a pump flange ( 10 ). Retaining elements ( 34 ) are provided for this connection. To avoid a twisting of the retaining elements ( 34 ) in the event of a damage, such as the blocking of the rotor ( 14 ) and the high moments occurring thereby, the retaining element ( 34 ) comprises an anti-twist structure ( 40 ) cooperating with the vacuum chamber housing ( 26 ).

BACKGROUND

The invention is directed to a vacuum pump arrangement, in particular a turbomolecular pump arrangement.

Vacuum pumps, such as turbomolecular pumps, for example, are connected to a vacuum chamber housing to generate a vacuum in a vacuum chamber. The connection is achieved with a pump flange connected to the pump housing and with corresponding retaining elements such as so-called claws, for example. These claws are connected with the pump flange, a lug of the claw engaging a groove or flute of the pump flange, for example. The claws are fastened to the vacuum chamber housing by means of a screw. Since such vacuum pumps weigh up to 65 kg and the rotor situated in the pump housing can reach numbers of rotations in the range from 30,000 to 100,000 rpm, safety must meet with high demands. Because of the great weight and the high rotor speeds, a safe fastening of the vacuum pump at the vacuum chamber housing has to be guaranteed to exclude hazards to operating personnel with great certainty. Especially in the event of a damage by a blocking of the rotor, high moments instantaneously occur that are transferred from the rotor to the pump housing via the stator and from the pump housing to the vacuum chamber housing via the claws. With such high moments, which may be on the order of several thousand Nm, the pump housing may be twisted relative to the vacuum chamber housing. This may cause damages to the vacuum chamber housing in the area where the claws are mounted. A damage to the vacuum chamber housing is a particular disadvantage, since in addition to replacing the vacuum pump, it is also necessary to repair the vacuum chamber housing. This does not only incur high costs, but may also interrupt production possibly for a longer time. It could possibly also happen that the claws break completely at the pump flange and that the vacuum pump is no longer held to the vacuum chamber housing so that the vacuum pump can drop. Besides damages to the vacuum chamber housing, this causes a high risk of injuries to the operating personnel.

Studies have shown that the above problems can occur especially with flange diameters of and larger than 160 mm.

It is an object of the present invention to increase the safety of vacuum pump arrangements in cases of damage.

SUMMARY

The present vacuum pump arrangement, which is a turbomolecular pump arrangement, in particular, especially comprises a pump of great weight and/or high speeds of rotation of the rotor. The vacuum pump arrangement has a pump housing in which a rotor and a stator are arranged. Connected to the pump housing is a pump flange that may also be configured directly as a part of the housing. Retaining elements are provided for fastening the pump housing to a vacuum chamber housing. According to the invention, at least one retaining element has an anti-twist means cooperating with the vacuum chamber housing. Providing such an anti-twist means ensures that in case of a damage, especially upon an instantaneous blocking of the rotor, no twisting of the retaining elements such as the claws will occur due to the occurring high moments. This especially avoids a loosening of the connection between the pump flange and the vacuum chamber housing so that the safety is enhanced. Further, the risk of a damage to the vacuum chamber housing in the region of the fastening of the retaining element is reduced.

Preferably, at least one retaining element with a present anti-twist means is provided. Preferably, two, especially oppositely arranged retaining elements with an anti-twist means are provided. Here, the present retaining element with an anti-twist means can be combined with conventional single retaining elements. Preferably, a plurality of retaining elements with an anti-twist means are provided, especially (together) with at least three retaining elements distributed along the circumference of the pump flange. The pump flange is preferably of annular shape.

As an anti-twist means, the retaining element may have a pin preferably engaging a recess or bore provided at the pump chamber housing. Additionally, the retaining element preferably has a fastening element, such as a screw. A preferred embodiment of the present retaining element thus comprises an anti-twist means, e.g. in the form of a pin engaging a recess, and a fastening element screwed into a thread provided in the vacuum chamber housing. In another preferred embodiment, the anti-twist means is also designed as a fasting element, especially a screw, so that the present retaining element has at least two, especially identically designed fastening elements. Since both fastening elements engage recesses, such as threaded bores, in the vacuum chamber housing, both fastening elements serve both fastening and anti-twist purposes.

The pump flange connected to the pump housing or formed as a part of the pump housing preferably comprises an annular groove. This groove may be discontinuous, but preferably extends along the entire circumference. The retaining elements preferably have a projection, especially in the shape of a segment of an annulus, engaging the groove. This substantially facilitates the mounting of the pump since the position of the pump housing relative to the vacuum chamber housing can be varied without having to change the position of the retaining elements.

Preferably, the radius of the groove substantially corresponds to the radius of the projections. In particular, this has the advantage that upon the occurrence of a very high moment in a case of damage the pump housing can rotate with respect to the retaining elements as soon as the forces acting due to the existing moment between the pump flange and the projections are greater than the frictional forces in this region.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a detailed description of a preferred embodiment of the invention with reference to the accompanying drawings.

In the Figures:

FIG. 1 is a schematic sectional view of a vacuum pump arrangement,

FIG. 2 is a schematic perspective view of a pump housing,

FIG. 3 is a schematic perspective view of a retaining element of the present invention, and

FIG. 4 is a schematic top plan view on a part of a vacuum pump arrangement with a retaining element according to prior art in a case of damage.

DETAILED DESCRIPTION

A vacuum pump arrangement comprises a pump housing 10 in which a rotor 14 rotating about a longitudinal axis 12 is arranged. Stator blades 16 connected to the housing 10 are disposed between the individual rotor blades 14. The rotor 14 is rigidly connected to a drive shaft 20 through a connecting element 18. The stator 16 is correspondingly rigidly connected to the housing 10 through a connecting element 22.

To create a vacuum in a vacuum chamber 24, the housing is fastened to a vacuum chamber housing 26 in the region of an opening 28.

For fastening, the housing has a pump flange 30 which in the embodiment illustrated is annular. The pump flange 30 has a L-shaped cross section so that an annular groove 32 is formed.

Using a retaining element 34, the pump housing 10 is fastened to the vacuum chamber housing 26 by the flange 30. To this end, the retaining element 34 in the embodiment illustrated has a projection 36, in particular in the shape of a ring segment, engaging the groove 32 of the pump flange 30.

As a fastening element, a screw 38 is provided for fastening the retaining element 34 to the vacuum chamber housing. Here, the present retaining element 34 (FIG. 2) comprises an anti-twist means 40, both the fastening element 38 and the anti-twist means 40 being designed as a screw in the embodiment shown. The anti-twist means 40 engages a recess 42, which, in the embodiment illustrated, is a threaded bore in the vacuum chamber housing 26.

Since the present retaining elements 34 have an anti-twist means 40 besides the fastening element 38, it is ensured in the event of a damage that no twisting of the fastening elements will occur. Despite the high moments prevailing in case of a damage, such as in a blocking of the rotor 14, which are transferred from the rotor 14 to the pump housing 10 via the stator 16, the retaining elements 34 are not twisted as could happen with corresponding single retaining elements 44 (FIG. 2).

The perspective view of the pump housing 10 in FIG. 2 is a view to the flange side of the pump housing with four retaining elements 34 of the present invention and four single retaining elements 44 being provided on the annular flange 30. The present retaining elements 34 each have an annular projection 36 engaging the groove 32 of the pump flange (FIG. 1). Further, two screws 38, 40 are provided per retaining element 34 that serve as a fastening element and an anti-twist means.

The screws 38, 40 are passed through throughbores 46 provided in the retaining element 34.

To clearly illustrate the prior art, FIG. 4 shows a single retaining element 44.

The single retaining element 44 is fastened in the vacuum chamber housing 10 by a screw 48. Due to the high moments occurring in the event of a damage, the pump housing 10 is rotated in the direction of the arrow 50. Thereby, a single retaining element 4 is twisted counterclockwise. This can cause damage to the flange 30 as well as to the vacuum chamber housing 26.

The invention has been described with reference to the preferred embodiments. Modifications and alterations may occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be constructed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof. 

1. A vacuum pump arrangement, comprising: a rotor and a stator, both arranged in a pump housing, a pump flange connected to the pump housing, and at least one retaining element connected to the pump housing and to a vacuum chamber housing for fastening the pump housing to the vacuum chamber housing, the retaining element being connected to an anti-twist means cooperating with the vacuum chamber housing.
 2. The vacuum pump arrangement of claim 1, wherein the anti-twist means engages a recess provided in the vacuum chamber housing.
 3. The vacuum pump arrangement of claim 1, wherein the retaining element comprises a fastening element provided in addition to the anti-twist means.
 4. The vacuum pump arrangement of claim 1, wherein the anti-twist means is additionally designed as another fastening element.
 5. The vacuum pump arrangement of claim 1, wherein at least three retaining elements are provided along the circumference of the pump flange.
 6. The vacuum pump arrangement of claim 1, wherein the pump flange has a groove in which engages a projection of the retaining element.
 7. The vacuum pump arrangement of claim 1, wherein the vacuum pump arrangement includes a turbomolecular vacuum pump arrangement.
 8. The vacuum pump arrangement of claim 5, wherein the pump flange is annular.
 9. The vacuum pump arrangement of claim 8, wherein the annular flange defines an annular groove.
 10. The vacuum pump arrangement of claim 9, wherein the retaining element includes a ring segment-shaped projection that is received in the annular groove.
 11. A vacuum pump comprising: a pump housing; a rotor and a stator disposed in the pump housing; an annular flange extending from the pump housing, the flange having: a vacuum chamber engaging face, and an annular groove defined in a face opposite to the vacuum chamber receiving face.
 12. The vacuum pump of claim 11, further including: at least one retaining element for engaging the face of the annular flange opposite the vacuum chamber, the retaining element having a fastening element for fastening the retaining element with the vacuum chamber and an anti-twist element which blocks the retaining element from rotating around the fastening element.
 13. The vacuum pump of claim 12, wherein the retaining element includes an arcuate projection that is received in the flange annular channel.
 14. A retaining element for retaining the vacuum pump of claim 11 to a vacuum chamber, the retaining element including: an arcuate leg that engages the face of the annular flange opposite to the vacuum chamber; an arcuate projection extending from the arcuate leg to engage the annular groove; an aperture which receives a fastening element; and an anti-twist structure that cooperates with a vacuum chamber housing to block the retaining element from rotating around the fastening element in response to high moments resulting from a vacuum pump failure. 